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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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Discussion Starter · #1 ·
My belt squeaks on startup and when I rev it hard as well as a chirp that pretty much becomes constant when driving. I recently have done a Saginaw pump 3g alternator and switched the underdrive crank pulley to the factory one. And wow what a difference with that. I also switched back to the stock water pump pulley because it had an aluminum one on it. I would say it started after the 130 amp alternator but it already had the 95 amp 3g on it. I got the 130 off a 1996 van. Could it be the alternator not aligned properly. I haven’t checked today because it’s been 40 and raining. Also is there a way to check what pulley it’s slipping on.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #2 ·
I put a breaker bar between the alternator and tensioner to use as a straight edge and the alternator is in compared to the tensioner by quite a ways. Can I just fix this with washers? If so anyone know what size. Or maybe my old pulley from the 95 amp.
 

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I’ve read there’s a recommended 0.050” shim to stick behind the pulley on some 3G conversions but I don’t recall the details.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #4 ·
I’ve read there’s a recommended 0.050” shim to stick behind the pulley on some 3G conversions but I don’t recall the details.
It seemed like it was off a little more then that.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #5 ·
Put a washer to move the pulley out and it didn’t fix it. I’m gonna try and put the old alternator on to see if that fixes it. It is slipping on the alternator as I can see the pulley being worn away.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
Any reason you put the underdrive crank pulley on? I know they used to be popular in the mustang world, but not sure they're of any real value on the Bronco and it could be contributing to your problem..I'd go back to the factory drive pulley and may sure you have a good belt tensioner. That's important with 3G alternator because they pull more at start up, but it should quiet down after it's running..FWIW, I did not use any shim on the pump pulley when I did the sag swap and never had an issue with squealing.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #7 ·
Any reason you put the underdrive crank pulley on? I know they used to be popular in the mustang world, but not sure they're of any real value on the Bronco and it could be contributing to your problem..I'd go back to the factory drive pulley and may sure you have a good belt tensioner. That's important with 3G alternator because they pull more at start up, but it should quiet down after it's running..FWIW, I did not use any shim on the pump pulley when I did the sag swap and never had an issue with squealing.
I took off the underdrive pulley that my dad put on it and put a stock one on it. I’ve replaced the belt tensioner before. What are signs that it’s bad.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
There's no real outward sign the tensioner is bad, usually if the belt is squealing that's a pretty good sign.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #9 ·
There's no real outward sign the tensioner is bad, usually if the belt is squealing that's a pretty good sign.
Any brand recommendation to go with. Would motorcraft be the best bet. Or possible one from a junkyard to try out. My junkyard is very cheap.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
Motorcraft is always good, but not inexpenive..typically I stick with motorcraft for sensors or any electronic related parts..If I recall there are two styles of tensioners, one preferred over the other..I have a dayco brand, looks like this one..I also replaced the plastic idler pulley with a metal one. Personally I wouldn't bother with the JY for a part like this, chances are you'll just get a piece of junk, but if the price is cheap and you want to give it a shot it can't hurt..

 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #11 ·
Motorcraft is always good, but not inexpenive..typically I stick with motorcraft for sensors or any electronic related parts..If I recall there are two styles of tensioners, one preferred over the other..I have a dayco brand, looks like this one..I also replaced the plastic idler pulley with a metal one. Personally I wouldn't bother with the JY for a part like this, chances are you'll just get a piece of junk, but if the price is cheap and you want to give it a shot it can't hurt..

I’ll get a dayco one from rockauto and hopefully that fixes the belt squeak. I also don’t have an idler pulley.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
how do you not have an idler pulley? It's part of the belt tensioner.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #13 ·
how do you not have an idler pulley? It's part of the belt tensioner.
Ah I thought you meant the idler pulley the newer trucks have. Yeah the pulleys fine. I’ll check and see what pulley it’s squeaking on this week.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #14 ·
Haven’t been able to go to the junkyard since I got a new job and have been working like crazy. I just bought a dayco one off rockauto. Hopefully it’ll be here this week and maybe I’ll get some time off of work on it this weekend. That belt squeak is horrible. Also is a sign of a bad tensioner one that sorta jumps a lot or tweaks up and down while the engine is running.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
Yes, a crappy tensioner will bouce around a lot..just replaced mine yesterday...
175047
 

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Registered
1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #16 ·
Yes, a crappy tensioner will bouce around a lot..just replaced mine yesterday...
View attachment 175047
Did that fix your belt squeak. Also what pulley was it squeaking on. My tensioner also mounts underneath the alternator not to the right of it.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
I didn't have a belt squeak yet, but the tensioner was making a knocking sound and bouncing all over the place..my pulleys are fine..it's possible to have a bad pulley but your tensioner is good..I'd say more than likely the squeak is related to the tensioner failing.
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #18 ·
I didn't have a belt squeak yet, but the tensioner was making a knocking sound and bouncing all over the place..my pulleys are fine..it's possible to have a bad pulley but your tensioner is good..I'd say more than likely the squeak is related to the tensioner failing.
Replaced it and that wasn’t the problem. It squeaks at the crank as well. So now I’m thinking there’s to big of a gap to bridge between the alternator and crank pulley or the crank pulley is out of alignment. Which I would need to fix with a different spacer since I have a aftermarket harmonic balancer. Also how would I find the ac idler pulley to use as the proper bigger pulley if I did a smog pump idler pulley. And what smog pump should I use. The only one I could find was the Ford performance one.

heres a video IMG_0318.MOV
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,146 Posts
I can't speak to the question about the smog pump, I don't have one on my rig..Are you sure you have the right size belt? is it possible your belt it just a little too big?

actually I think that's your problem..looking at your video, the belt looks like it's loose..
 

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1987 Ford Bronco, beefed up 351w, JBG HD rear springs, JBG 4” coil, 10.25 rear posi, Dana 44 posi
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426 Posts
Discussion Starter · #20 ·
I have a 98 1/8” belt on it right now. Another thread about smog pump delete as the same exact route as mine but his was 97 1/8” belt. The only difference between my setup and that guys was mine has a Saginaw pump which I think as a slightly bigger pulley. I also don’t think I could find a smaller belt size that would fit. If you can please do.
 
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